Update the nix build configuration.

Remove the old shell.nix with some legacy versions pinned and replace it with a flake-based shell. It installs rust via rustup instead of fenix to be more generally compatible with the guidelines.

This also adds the rust-toolchain.toml spec with all the components required for wasm, and everything else to make rust-analyzer & clippy happy.

.gitignore

@@ -27,3 +27,4 @@ rls*.log
 scripts/ci/node-template-release/Cargo.lock
 bin/node-template/Cargo.lock
 substrate.code-workspace
+.direnv/

bin/node-template/.envrc

@@ -0,0 +1 @@
+use flake

bin/node-template/flake.nix

@@ -0,0 +1,24 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, ... }: flake-utils.lib.eachDefaultSystem (system:
+    let
+      pkgs = import nixpkgs { inherit system; };
+    in
+    {
+      devShells.default = pkgs.mkShell {
+        packages = with pkgs; [
+          rustup
+          clang
+          protobuf
+          rustfmt
+        ];
+        shellHook = ''
+          export LIBCLANG_PATH="${pkgs.libclang.lib}/lib"
+        '';
+      };
+    });
+}

bin/node-template/rust-toolchain.toml

@@ -0,0 +1,14 @@
+[toolchain]
+channel = "nightly"
+components = [
+	"cargo",
+	"clippy",
+	"rust-analyzer",
+	"rust-src",
+	"rust-std",
+	"rustc-dev",
+	"rustc",
+	"rustfmt",
+]
+targets = [ "wasm32-unknown-unknown" ]
+profile = "minimal"